Canon EDS 30D Viewfinder Off during Picture Taking Works to Display Picture Taken How do I turn back on?

The EOS 30D does not have "live view". (Most SLR digital cameras made before 2007 do not.) By definition, an SLR (single lens reflex) camera looks through the same lens with the viewfinder as it uses when taking the picture.

So there is no way to see the picture on the LCD before the picture is taken, like you can with compact digital cameras. You compose the picture through the optical viewfinder, then shoot.